Process of blending a polyvinyl chloride plastisol with molten coal tar pitch



United States Patent Reuben Sperling, London, England, assignor to The Ruberoid Company, London, England No Drawing. Application May 20, 1953 Serial No. 356,299

Claims priority, application Great Britain November 20, 1952 Claims. (Cl. 260-285) This invention relates to the production of bituminous compounds which are heat and solvent resistant, and which have several desirable characteristics including elasticity, pliability, and a consistency which does not change rapidly with temperature. These compounds can be used as sealing compounds for expansion and contraction joints on concrete runways used by jet aircraft, also as coatings for sheet materials which are required to be resistant to the destructive action of jet engine exhausts, as an ingredient in the manufacture of asphaltic carpets which are required to be heat and solvent resistant, and as a flooring material.

The invention consists in adding 1-100 parts by weight, and especially about 10 parts, of a mixture of polyvinyl chloride and a plasticiser to 100 parts of a molten mixture, the principal ingredient (that is, at least 50%) of which is coal tar pitch, and then stirring the whole mixture until it becomes substantially homogeneous.

The polyvinyl chloride should be very finely dispersed in its plasticiser to form a paste (i.e. a plastisol), generally containing -50% of polyvinyl chloride. The plasticiser can be any of those materials which are capable of plasticising polyvinyl chloride satisfactorily. Examples of such plasticisers are tricresyl phosphate, tritolyl phosphate, dibutyl phthalate, and dioctyl phthalate.

The coal tar pitch may be derived from any of the recognised sources of coal tar pitches including those from the high temperature carbonisation of coal in horizontal, inclined or vertical retorts, also those from the low temperature carbonisation of coal.

It may be softened or plasticised with road tar, creosote oil, anthracene oil, heavy oil, heavy naphtha, and low melting coumarone and indene resins.

The temperature and mixing time will depend upon r, the nature of the coal tar pitch mixture, but in general the temperature should be at least C. above its softening point, and yet must not be so high that the pitch is hardened unduly through the action of heat. The time required to produce a homogeneous mixture may vary from a few minutes to one or two hours.

These bituminous compounds may be further improved by incorporating fillers in the form of powders or fibres.

Examples of such fillers are slate powder, asbestos fibre, china clay, whiting, cotton linters, and slag wool.

The expression coal tar pitch should be understood as including the chemical equivalent of natural coal tar pitch, derived from the cracking of petroleum under conditions giving rise to aromatisation; this equivalent is, in effect, a synthetic coal tar pitch. The expression pitc signifies a thermoplastic, non-distillable bituminous solid, and the range of so-called pitches commercially available consist in pitch proper admixed with varying amounts of oil, especially residues of anthracene oil, heavy oil and the like which have escaped distillation during the isolation of the pitch. These pitches exist in a continuous range, from substantially oil-free hard pitch in the following examples:

2,883,354 Patented Apr. 21, 1959 downto products which are soft at room temperature; beyond this, with increasing oil contents, the material is generally termed tar. Whichever of these sources of pitch isemployed, theproportion relative to the polyvinyl chloride is calculated on an oil-free basis.

Various embodiments of this invention are described Example 1 I 100,parts by weight of a coal tar pitch having a ring and ball softening point of 42 C. are heated to 130 C., and 10 parts by weight of a paste (i.e. a plastisol) comprising 40% polyvinyl chloride and 60% tritolyl phosphate are added to the well stirred pitch. After mixing for 20 minutes the mixture becomes smooth and apparently homogeneous. The product is an elastic pitch having a ring and ball softening point of 55 C. and a penetration at 25 C. of 65.

By adding 20 parts by weight of short asbestos fibres to the molten product, the ring and ball softening point is increased to 68 C. and the penetration at 25 C. is decreased to 34. The addition of the asbestos fibre increases the resistance of the material to flow at elevated temperatures without impairing its elasticity.

Example 2 parts by weight of a coke oven pitch having a ring and ball softening point of 62 C. are blended with 5 parts by weight of a liquid grade of coumarone resin to give a mixture having a ring and ball softening point of 52 C. 10 parts by weight of a paste (i.e. a plastisol) comprising 40% polyvinyl chloride and 60% tritolyl phosphate are added to the molten well stirred mixture maintained at C. After stirring for 15 minutes a smooth pitch is obtained having a ring and ball softening point of 61 C. and a penetration at 25 C. of 20.

Example 3 100 parts by weight of a coal tar pitch having a ring and ball softening point of 30 C. are heated to C. and 50 parts by weight of a paste (i.e. a plastisol) comprising 40% polyvinyl chloride and 60% tritolyl phosphate are added to the well stirred pitch. After stirring for 5 minutes a smooth mixture is obtained having a ring and ball softening point of 126 C. and a penetration at 25 C. of 54.

I claim:

1. A process for the production of a bituminous compound which comprises blending 1 to 100 parts by weight of a plastisol containing polyvinyl chloride and a plasticiser, with 100 parts by weight of molten coal tar pitch, by stirring the plastisol into the molten pitch.

2. A process as set forth in claim 1, in which about 10 parts by weight of the plastisol are employed.

3. A process as set forth in claim 1, in which the plastisol contains 30-50% of polyvinyl chloride.

4. A process as set forth in claim 1, in which the plasticiser used is selected from the group consisting of tritolyl phosphate, tricresyl phosphate, dibutyl phthalate and dioctyl phthalate.

5. A process as set forth in claim 1 in which the pitch is admixed with a softener selected from the group consisting of creosote oil, anthracene oil, heavy naphtha and low melting coumarone indene resins.

6. A process as set forth in claim 1, in which an inert filler is incorporated in the bituminous compound.

7. A process as set forth in claim 1, in which the blending by stirring is carried out at a temperature at least 5 0 C. higher than the softening point of the pitch before the addition of the plastisol.

8. A process for the production of a bituminous compound which comprises stirring parts of a plastisol containing 40% of polyvinyl chloride and 60% of tritolyl phosphate into 100 parts of a molten coal tar pitch, thereafter incorporating parts of short asbestos fibre.

9. A process for the production of a bituminous compound which comprises blending 95 parts of coke oven pitch with 5 parts of a liquid coumarone resin and thereafter stirring into the molten mixture, 10 parts of a plastisol containing of polyvinyl chloride and 60% of tritolyl phosphate.

10. A process for the production of a bituminous compound which comprises melting 100 parts of a coal tar pitch having a ring and ball softening point of 30 C.

and stirring in parts of a plastisol containing 40% polyvinyl chloride and of tritolyl phosphate.

References Cited in the file of this patent UNITED STATES PATENTS 2,464,219 Doyle et a1 Mar. 15, 1949 2,464,263 Rudd Mar. 15, 1949 2,635,085 Gonnard et al Apr. 14, 1953 2,715,615 De Bell et a1. Aug. 16, 1955 FOREIGN PATENTS 602,582 Great Britain May 28, 1948 

1. A PROCESS FOR THE PRODUCTION OF A BITUMINOUS COMPOUND WHICH COMPRISES BLENDING 1 TO 100 PARTS BY WEIGHT OF A PLASTISOL CONTAINING POLYVINYL CHLORIDE AND A PLASTICISER, WITH 100 PARTS BY WEIGHT OF MOLTEN COAL TAR PITCH, BY STIRRING THE PLASTISOL INTO THE MOLTEN PITCH. 